**6.3. Simplification of commercial cultivar**

Cultivars (ROC10, ROC16, and ROC20) from Taiwan Sugar Co-operation were grown in more than 70% of the total sugarcane plantation area, while varieties bred in mainland China were less than 30% in the past 30 years. ROC 22 has been planting more than 50% of sugarcane growing area in China over 20 years. This variety is becoming more susceptible to smut and cold, and poor ratooning ability. Especially, after continuous cultivation of ROC22 in the same fields, the soils have accumulated considerable amounts of smut pathogens. That is why healthy seed cane application for ROC22 does not give expected good results in sugarcane production. Finally, the sugarcane ratooning is limited to 1 or 2 years in China, when compared to Brazil where the production cycle is over 5 years.

#### **6.4. Frequent stresses on sugarcane production**

Sugarcane production often suffers from the biotic and abiotic stress in China [35, 36]. For example, the frost in 1998–1999 and the drought in 2005–2006 caused serious damage to sugar production. Sugarcane smut, Pokkah Boeng, ratoon stunting, mosaic, and other diseases caused more than a 20% reduction in production. Borers and soil-borne pests (e.g., *Dorysthenes granulosus*, grub) were found in over 60% of sugarcane plantations, which caused the loss of sugar content of over 0.5%.

### **6.5. Prospect and solutions of Chinese industry**

CY 2016 is the first year of China's governmental five-year plan (2016–2020) to boost sugar production. The plan's target is to raise annual sugar production to 15 MMT by 2020, when consumption is forecast to reach 18 MMT. The plan also implies the government's intention to gradually reduce imports. Sugar production needs to increase more than 10% annually from 2016 to 2020 in order to meet these challenging policy targets. The government has stated that it will provide subsidies and financial support to farmers to increase yields and reverse declines in sugarcane acreage. The Guangxi government has already started providing subsidies of \$5625 per hectares for seeds to sugarcane farmers, farm machinery, mulching film, and fertilizer. The goal is to reach 333,300 ha of "double-high" (high in sugar content and yield) sugarcane. "Double-high" production is classified as a yield of at least 120 MT per hectare and sugar content at 14% or more by constructing the sugarcane production base for optimization of cultivars, mechanization of production, modernization of water conservancy, and operation at large scale [37]. Currently, in Guangxi province, sugarcane production is under 75 MT per hectare and sugar content is 12%. So, there is a long way and urgent issue to go for sugarcane production in China, including breeding cultivars for mechanical harvest and planting sugarcane at economical and efficient production.

To date, no complete sugarcane genome sequence has been reported, which restricts the development of functional genomics and modern breeding. Omics-based sugarcane breeding will benefit sugarcane production by shortening breeding duration and increasing selection efficiency, including transgene, genomic edit, and marker-assisted selection [38–40]. They have created much enthusiasm to identify genetic components of traits, particularly quantitative traits, in Mendelian factors, and to monitor or direct their changes during breeding through omicsbased selection.
